Tap guide



R. E. ASHTON May 29, 1951 TAP GUIDE Filed Jan. 3l, 1946 INVENTOR RALPH E. /lsHTo/v BY ATTORFV Patented May 29', 1951 UNITED STATES "2" OFFICE 1 Claim.

This invention relates to mechanics tools and facilities of hand or bench type, and more particularly to auxiliary means for selective association with conventional thread-cutting taps to guide and position the latter during use for improved quality and precision of results, and has as an object to provide an improved construction and cooperative arrangement of elements constituting such means.

A further object of the invention is to provide an improved guide for thread-cutting taps that is readily and conveniently adaptable to` association and effective use with a wide range of specific tap sizes and lengths.

A further object of the invention is to provide an improved tap-guide susceptible of correlation with the shank sizes and lengths of conventionally standardized tap sets.

A further object of the invention is to provide an improved separable tap-guide construction whereby a single major element of they improvement is adapted to and for use with taps of differing shank sizes and lengths.

A further object of the invention is to provide an improved tap-guide having immediately interchangeable elements sized to receive and cooperate with taps of diiiering shank sizes and lengths.

A further object of the invention is to provide an improved separable tap-guide characterized by novel and eilicient means for interengaging and frictionally holding the complementary elements of the device in operative relation with each other.

A further object of the invention is to provide an improved tap-guide that is simple and inexpensive of manufacture, sturdy and durable in construction, elective to accomplish the ends for which designed, and facile of use.

With the foregoing and other objects in view,

' my invention consists inthe construction, ar-

rangement, and combination of elements hereinafter set forth, pointed out in my claims, and illustrated by the accompanying drawing, in which- Figure 1 is a vertical section taken axially through a typical embodiment of the invention as positioned in operative association with a con.- ventional thread-cutting. tap for' practical; use relative to a flat surface. Figure 2` is a section similar to Figure 1 depicting an alternative arrangement and use of the invention. Figure 3 is a top plan View of. the improved tap-guide major element freed from association with its interchangeably employable with the tap-guide' major element. Figure 6 is a view similar to Figure 5 illustrating the elements of the latter showing in side elevation.

Internal screw-threading of cylindrical holes in and' through sections of rigid material is a common and recurrent operation incident to the construction, assembly, maintenance, and repair of a multitude of structures and devices. Except in the case of certain initial constructions, internal screw-threading is extensively accomplished by means of manually-actuated hand or bench tools known as taps, which, in a variety of typesand speciiic constructions Well standardized as to thread form, pitch and diameter, shank diameter, and overall length, are normally ineluded in the kits of well-equipped mechanics. Hand manipulation of conventional taps for the production of smooth, uniform screw threads in properV relation with the work stock is onerously diicult, particularly when the stock section to be threaded is thin, because of the necessity for maintaining the' tap in axial coincidence with the hole being threaded while simultaneously rotating the tap about its axis; the manipulated end of the tap remote from` the work stock tending to wander through a more or less" circular orbit or to incline away from the desired axial coincidence, with consequent thread deformation orV mislocation, as the tap is rotated. To obviate the diiiiculti'es and disadvantages above noted, and t'o facilitate the production of true, high quality threads by means of hand-actuated taps, the improved guide of the instant invention has been developed. Y

In the construction of the improvement as shown, the numeral l!! designates a straight, tubu-lar member formed of any suitable hard, rigid material, such as metal, and with its axial bore opening through both of its' ends. the' member |10' is worked or formed, in any con- One end of venient manner, to provide an integral, circumferentially-exterior flange II whereof the outer or free face is trued to a plane perpendicular to the member I axis, said flange II hence constituting a base or foot for the support of the member I0 on and in axially-perpendicular, upstanding relation with any fiat surface. The member I0 is preferably relatively thick-walled, sized to a bore diameter such as will freely receive and accommodate a substantial range of tap sizes, and has a length sufficient to house the thread-cutting portion of work-engaged standard taps receivable therein, the shank and angular tool-receiving head of the tap projecting axially of and outwardly beyond said member when the flange II of the latter is in bearing relation against the work stock. The end of the member I0 remote from its iiange II is reduced in ex terior diameter to form an integral, thinnerwalled extension I2 axially-coincident with and traversed by the member bore, which extension is adapted to telescopically cooperate with and removably and replaceably mount a tap-aligning cap in closing relation with said member end.

To accommodate differences in overall lengths of standard taps otherwise cooperable with a given member ID, the member end caps are of two distinct types, and to accommodate differing tap shank sizes, said caps, regardless of type, are proi vided in suitable number whereof each has a concentric, cylindrical bore sized to rotatably accommodate and serve as a guide bearing for a particular tap shank size. With the longer taps, typically represented at I3 in Figure 1, it is feasible and convenient to utilize a cap I4 having a relatively-thick base web, a cylindrical exterior surface conforming with that of the member I0, an annular marginal ange extending axially from the base web under surface to telescope snugly over and enclose the member end extension I2, and a concentric, cylindrical hole axially through the base web and of a size to t smoothly about and rotatably accommodate a tap shank of particular size, such a cap completing the operative tap guide for association and use with a' longer tap I3 in the manner clearly shown in Figure 1. Caps I4 may be provided for interchangeable use with a given member I0 in such number and assortment of base web hole sizes as may be feasible to operatively accommodate and guide the longer taps of any particular tap set or supply, the cap arranged to telescope exteriorly over the member I0 and being especially desirable in that its bearing for the shank end is thereby positioned at a maximum spacing from the work stock and hence for most eflicient functioning as a guide in maintaining the tap in axial coincidence with the hole being worked. For use with shorter taps, represented at I5 in Figure 2, and where use of a cap I4 would not permit sufcient range of axial tap travel, a cap of the type indicated by the numeral I6 may be employed with the member I0 for functional effect the same as provided by the cap I4. The cap I6 is designed to telescope interiorly of the member I Il end extension I2 and to provide aguide bearing for a tap shank without unduly increasing the guide assembly length, for which purpose said cap I6 is formed with a relatively-thin base web adapted to overlie and engage against thel end of the extension I2, a cylindrical, concentric b'oss projecting axially from its base web underv side and of a diameter to telescope snugly within the extension I2, and a concentric, cylndrifl.

hole axially through said boss and of a size to fit smoothly about and rotatably accommodate a tap shank of particular size, said cap I6 hence serving to provide a guide bearing for the tap shank at the end of the member I0 remote from the work stock in essentially the same manner as the interchangeable cap I4, but in relatively diminished spacing from the member iiange II.

To minimize accidental separation of a selected cap I4 or I6 from mounted association with the member I Il, while preserving facility of cap interchangeability, means are provided for automatically maintaining a resiliently-yieldable frictional grip between the extension I2 and the cap of either type associated therewith, said means conveniently taking the form of a slot or kerf I1 longitudinally intersecting and opening through the end of the said extension I2, and slightly skewed or twisted corners on said extension where said slot I'I intersects the extension outer end, one of said corners being twisted to outwardly overhang the extension outer wall, as indicated at I8 in Figure 3, in position to grip and frictionally hold interiorly of a cap I4 annular ange telescoped over the extension, and the other of said corners being twisted to inwardly overhang the extension inner wall, as indicated at I9 in Figure 3, in position to grip and frictionally hold exteriorly of a cap I6 cylindrical boss telescoped within said extension; said corners I8 and I9 readily springing under intentionally-applied pressures to permit removal and replacement of caps I4 and I6 relative to the member I0.

The improved guide assembly constructed and arranged as illustrated and described provides eflicient means cooperable with a tap to hold said tap in the desired perpendicular relation with flat surfaced work stock 20, the flanged end surface of the assembly engaging solidly against the work surface to brace the guide and minimize tilting thereof as the guide assembly is held in position by one hand of an operator and the tap is `rotatably manipulated by the operators other hand. Since it is frequently necessary to thread holes intersecting arcuate work stock surfaces, typically represented by the showing of cylindrical stock 2I in Figure 2, it is convenient to form a V-shaped notch 22 diametrically across and in intersecting relation with the otherwise plane flange I I free end, which notch serves in an obvious manner to seat the guide assembly Irelative to an arcuate Work surface and to thereby brace said assembly to a considerable and helpful extent. End intersections of the notch 22 with the flange II take the form of V-shaped openings through which access may be had for the introduction of lubricants to the cutting elements of the tap and for the escape of chips from the member I0 interior.

Since many changes, modifications, and variations in the specific form, construction, and arrangement of the elements shown and described may be had without departing from the spirit of my invention, I wish to be understood as being limited solely by the scope of the appended claim, rather than by any details of the illustrative showing and foregoing description.

I claim as my invention:

In a tap guide having a rigid-walled, straightbore, tubular member formed with a work-engageable foot on one end, means adapting said member for guiding cooperation with a tap shank, said means comprising a coaxial, reduced-diameter extension on the end of said member remote ,from said foot, a cap removably, replaceably and REFERENCES CITED The following references are of record in the 15 le of this patent:

Number Number 6 UNITED STATES PATENTS Name Date Smith Mar. 6, 1894 Hearne Feb. 26, 1895 Gulick Jan. 12, 1897 McGrady Aug. 15, 1916 Muller July 13, 1920 Eisele Apr. 18, 1933 Cross July 16, 1935 FOREIGN PATENTS Country Date Great Britain Jan. 15, 1923 

